Photographic flashlamp unit

ABSTRACT

A multilamp photographic flashlamp unit, the lamps of which are of the percussive primer type, having self-contained firing elements each in the form of a self-latching folded torsional spring. The spring is shaped as a hairpin having two segments joined at the top by a bight with a supporting foot projecting from the lower end of one of the segments and a striker projecting from the bottom of the other segment for firing an associated lamp. One of the segments has a deformation just above the striker which tends to engage the other segment for stabilizing both the cocked position and arc of travel of the striker.

[451 May 23, 1972 [541 PHOTOGRAPHIC FLASHLAMP UNIT [72] Inventors: John W. Shatter, Williamsport; Thomas B.

McDonough, Allenwood, both of Pa.

[73] Assignee: GTE Sylvania Incorporated [22] Filed: Feb. 18, 197] 21 Appl. No.: 116,514

Primary Examiner-Louis R. Prince Assistant Examiner-Denis E. Corr AttorneyNorman J. OMalley, Edward J. Coleman and Joseph C. Ryan [57] ABSTRACT A multilamp photographic flashlamp unit, the lamps of which are of the percussive primer type, having self-contained firing elements each in the form of a self-latching folded torsional spring. The spring is shaped as a hairpin having two segments joined at the top by a bight with a supporting foot projecting from the lower end of one of the segments and a striker projecting from the bottom of the other segment for firing an associated lamp. One of the segments has a deformation just above the striker which tends to engage the other segment for stabilizing both the cocked position and are of travel of the striker.

5 Claims, 8 Drawing figures Patented May 23, 1972 2 Sheets-Sheet 1 PRIOR ART JOHN W. SHAFFER THOMAS B. MCDONOUGH INVENTORS BY f %M AG NT Patented May 23, 1972 3,665,176

2 Sheets-Sheet f;

FIG.6

JOHN w SHAFFER THOMAS B McDONOUGH INVENTORS gimgm AGE PHOTOGRAPIIIC FLASIILAMP UNIT BACKGROUND OF THE INVENTION This invention relates to multilamp photographic flash units, commonly called flashcubes, and moreparticularly to flashcubes having lamps of the percussive primer type and the means employed to fire them.

Generally speaking, a percussive-type photoflash lamp comprises a hermetically sealed, light-transmitting envelope containing a source of actinic light and having a primer secured thereto. More particularly the percussive-type photoflash lamp may comprise a length of glass tubing constricted to a tip at one end thereof and having a primer sealed therein at the other end thereof. The length of glass tubing which defines the lamp envelope contains a combustible such as shredded zirconium foil and a combustion-supporting gas such as oxygen. The primer may comprise a metal tube and a charge of fulminating material on a wire anvil supported therein. Operation of the lamp is initiated by an impact onto the tube of the primer to cause deflagration of the fulminating material on the wire anvil up through the tube to ignite the combustible disposed in the lamp envelope.

Heretofore, several different means have been suggested for firing these percussive-type flashlamps, many of which involve some form of spring mechanism built into the camera. More recently it has been suggested that the firing means be selfcontained within the body of the flashcube itself and a separate one of these means be provided for each of the lamps. Various forms and types of springs have been suggested for this purpose, one of the most practical being a folded torsion spring described in the co-pending application of J.W. Shaffer, Ser. No. 785,098, now US. Pat. No. 3,597,604, filed Dec. 19, i968, entitled Photographic Flashlamp Unit," and assigned to the same assignee as this invention. In accordance with the principles of that invention, each percussive-type flashlamp in the flashcube is provided with its own folded torsion spring to store the energy for firing it, with the tip of the stationary end of the spring shaped to function as a catch to hold the striker formed on the movable end thereof while the spring is in the cocked position. Displacement of the cocked striker to release it from the catch and thus permit it to strike the tube of the primer and fire the lamp is effected by a suitable finger or the like reciprocatively supported in a camera and arranged to move up through a slot provided therefor in the flashcube base to engage and displace the striker.

Considering the spring in more detail, see FIG. 1, it is formed from 0.021 inch diameter music wire about 2.2 inches long. The wire is shaped to define a hairpin torsional section having segments 3 and 5 and a bight 7. The end portion of segment 3 is shaped to define a stationary supporting foot 9, the tip of which is shaped to define a catch 1 1. The end portion of segment 5 is shaped to define a striker 13 which, when the spring is cocked as shown, crosses over the supporting foot 9 and is restrained by catch 11.

Efforts to substantially reduce the size of the percussivetype flashcubes have necessitated minimizing the diameter of the hairpin bight (i.e., the distance between segments 3 and 5 at the points where bight curvature begins). Upon evaluation, however, it has been observed that springs having a bight diameter less than 3% wire diameters present formidable problems with respect to cocking, storage and release. More specifically, when cocking the spring by rotating striker 13 from its initial pre-cocked position, represented by the dashed lines in FIG. 1, the torsional segment 5 crosses over torsional segment 3, as shown in FIG. 2. This permits the striker heel 15 to snap between torsional segment 3 and catch 11, thereby losing the cocking energy that was to be stored in the spring. Such crossover may also occur during storage and handling, even in springs that apparently have been successfully cocked. As a result of this unstable condition, automated spring cocking is precluded, thereby posing a significant impediment to the practical manufacture of miniaturized percussive flashcubes.

A further problem is presented when striker 13 is released from catch 1 I for purposes of firing one of the percussive flashlarnps. To assure reliable operation, the full stored energy of the torsion spring should be applied in striking the associated lamp primer tube. In the case of small bight diameter springs, however, striker 13 tends to deviate radially outward from the desired circular are about segment 3. As a result, the striker is prone to hit structural elements of the flashcube during its course of travel, whereupon a substantial amount of the stored spring energy would be dissipated prior to impact on the primer tube, resulting in faulty operation. I

SUMMARY OF THE INVENTION In view of the foregoing, one of the objects of this invention is to provide a flashcube having an improved form of folded torsion spring as the firing mechanism for the percussive-type flashlamps disposed therein.

Another object of the invention is to provide a flashcube with a firing spring that is much more stable than previous spring designs and is less subject to inadvertent loss of energy during cocking, storage or release.

A further object is to provide a firing spring which is particularly suitable for use in miniaturized percussive flashcubes.

A further object is to provide a torsion spring construction including a tightly folded hairpin bight which is compatable with automated assembly and cocking.

These and other objects, advantages and features are attained in accordance with the principles of this invention by the incorporation of an offset or undulation in one of the torsional segments of the self-latching, folded torsional spring, preferably adjacent to the striker between the bight and the striker. It has been found that this arrangement significantly stabilizes both the cocked position and are of travel of the striker, thereby assuring reliable flashcube operation and making possible the automated assembly and cocking of springs having relatively small diameter hairpin bights.

BRIEF DESCRIPTION OF THE DRAWINGS This invention will be more fully described hereinafter in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a prior art folded torsion spring to which reference has been previously made;

FIG. 2 is a perspective view of the spring of FIG. 1 in an improperly cocked condition, also referred to previously;

FIG. 3 is a perspective view of a flashcube embodying the principles of this invention;

FIG. 4 is a fragmentary view on an enlarged scale of a single lamp firing spring assembly of the flashcube of FIG. 3;

FIG. 5 is a plan view of the base of the flashcube of FIG. 3 with the several spring members shown in full and the several flashlamps associated therewith shown in phantom; and

FIGS. 6-8 are perspective views of alternative embodiments of the spring in FIG. 4.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to FIG. 3, the flashcube 20 comprises a substantially rectangular base 22 along each side of which a percussive-type flashlamp 24 is arranged. Each lamp 24 is provided with its own reflector 26 and the assemblage of lamps and reflectors is enclosed in a transparent container 28 secured to the base 22. Each lamp 24 comprises a hermetically sealed light transmitting envelope 30 having a primer depending therefrom and a filling of combustible foil 32 and a combustion-supporting gas disposed therein. The primer comprises a metal tube 34 within which an anvil and a charge of fulminating material are disposed.

As shown particularly in FIG. 4, the folded torsion spring 36 typically is formed from 0.021 inch diameter music wire. The wire is shaped to define a hairpin torsional section having segments 38 and 40 and a bight 42. The end portion of segment 38 is shaped to define a stationary supporting foot 44, the tip of which is shaped to define a catch 46. Portions of foot 44 and catch 46 are hidden in FIG. 4, however, the shape is the same as that of foot 9 and catch 11 in FIG. 1. The end portion of segment 40 is shaped to define a stroker 48 which, when the spring is cocked as shown, crosses the supporting foot 44 and is restrained by catch 46. The stationary supporting foot is seated in an elongated slot formed in the base 22 on or near a diagonal thereof, said slot being sufiiciently shallow so that the catch 46 formed on the free end of the foot 44 will project a relatively substantial distance above the plane of the top face of the base 22.

Initially, the striker 48 may be formed at an angle of about 90 to the stationary supporting foot 44, although the angle through which the striker is rotated to position it behind the catch 46, as shown, may be any value that does not cause overstressing of the wire. The center post 50 on the top face of the base 22 provides a suitable bearing surface for the heel of the striker during cocking, and it also aids in preventing accidental displacement of the spring 36 sufficient to free the striker from the catch sometime after cocking and before firing is intended.

in accordance with the principles of this invention, the lower portion of segment 40 of the hairpin torsional section of the folded torsion spring 36 is shaped to provide a deformation, in this instance an offset 52, for stabilizing both the cocked position and are of travel of striker 48. More specifically, offset 52 tends to engage segment 38 so as to restrain striker 48 from slipping radially outward. Thus, when the spring is cocked as shown, offset 52 retains the striker in form engagement with segment 38 and prevents the striker heel from inadvertently snapping between segment 38 and catch 46, as shown in FIG. 2. Accordingly, a much more stable spring construction is provided which substantially precludes inadvertent energy loss during storage and handling.

When the spring is being cocked, offset 52 causes the striker to be continuously retained in pivotal engagement with torsional segment 38 as the striker is being rotated about an arc of approximately 90 toward catch 46. This also prevent the FIG. 2 condition and particularly facilitates automated assembly and cocking, being especially advantages in the case of tightly folded torsion springs.

Displacement of cocked striker 48 to release it from the catch 46 and thus permit it to strike the tube 34 of the primer and fire the lamp, is effected by a suitable finger 54 or the like moving up through a slot 56 provided therefor in the base. The finger 54 may be part of a camera mechanism designed to enable a photographer to flash a lamp in synchronization with the tripping of the camera shutter to take a picture. Thus when the finger 54 pushes the striker 48 upwardly a distance suflicient to clear the top of the catch 46, the striker swings clockwise as shown by the arrow in FIG. 4 and hits and indents the impactsensitive primer tube 34 at high velocity to cause deflagration of the fulminating material located therein and thus ignite the combustible foil 32.

The bottom face of the base 22 of the flashcube 20 is provided with a suitable center post or the like (not shown) for mounting on a camera and providing a means whereby the flashcube may be rotated 90 after a lamp has been flashed so that another lamp may be advanced to firing position. As illustrated in FIG. 5, each of the four flashlamps 24 is provided with its own firing mechanism as shown in detail in FIG. 4 and described above. The hairpin torsional sections of the springs are clustered in the space behind the reflectors 26, with a clearance being provided along the lower edges of these reflectors to permit free operation of the strikers. With such compact package confines, however, there is very little tolerance for radially outward deviationof the striker in the course of its swing after release form catch 46. If unrestrained, interference from a wall of the container 28 or one of the reflectors 26 is quite probable, particularly in the case of tightly folded torsion springs, in which event there would be a premature dissipation of spring energy. Hence, an additional feature of offset 52 is that the restraining action it provides controls the travel of released striker 48 to define a substantially circular arc about segment 38, and thereby prevents the above mentioned undesirable effects.

Although the specific embodiment of FIGS. 4 and 5 depicts an offset in the movable torsion segment 40 from which the stroker projects, other forms of deformation, such as undulations, lobes, pinches and the like may be employed, and the deformation may be located in the stationary torsion segment 38 from which the foot projects. To provide the desired restraining action, however, it is preferred that the deformation be located substantially adjacent to striker 48 between the striker and bight 42. For example, FIG. 6 shows a folded torsion spring according to the invention in which the deformation in segment 40 comprises an undulation 58. FIG.. 7 illustrates a spring in which the deformation for restraining radially outward movement of the striker 48 comprises an offset 60 in the stationary segment 38. FIG. 8 is a variation of FIG. 7 in which an undulation 62 is employed in lieu of offset 60.

In all cases, the lateral excursion of the deformation, i.e., the depth of undulation or degree of offset, should be greater than one half the wire diameter but not more than four times that value. Very slight deformations give erratic performance, whereas excessive ofisets or undulation depths counteract the intended compactness of the spring.

Thus, it has been found that the tendency for undesired crossover of the torsion spring and the resulting cocking, storage and release difficulties can be eliminated by the provision of a deformation in one of the vertical torsional segments thereof. The principles of the invention are of particular value when the diameter of the hairpin bight 42 is 3% wire diameters or less so as to minimize the amount of space taken up by the springs in the percussive flashcube. In such case, the deformation permits automated spring cooking and makes the cocked spring more stable. Accordingly, the invention makes practical the automated manufacture of appreciably smaller percussive flashcubes.

What we claim is:

1. In a photographic flashlamp unit having a plurality of percussively-ignitable flashlamps with primer tubes depending therefrom mounted on a base, a folded torsional firing spring for each of said lamps disposed on said base, said firing spring comprising a substantially hairpin torsional section having two segments joined by a bight, a striker projecting from one of said segments, a supporting foot projecting from the other of said segments, and a catch formed at the tip of said foot, said striker crossing said foot and bearing against the segment from which said foot projects with said catch restraining said striker in a cocked condition, and one of said segments having a deformation located substantially adjacent to said striker between said bight and said striker, said deformation retaining said striker in firm engagement with the segment from which said foot projects.

2. The combination of claim 1 in which said deformation in one of said segment tends to engage the other of said segments whereby said striker is retained in pivotal engagement with the segment from which said foot projects during cocking of said striker and, upon release of said striker from said catch, the travel of said striker is controlled to define a substantially circular are about the segment from which said foot projects.

3. The combination of claim 1 in which the diameter of said bight of said spring is equal to or less than 3% times the wire diameter of said spring.

4. The combination of claim 1 in which the lateral excursion of said deformation is greater than one-half the wire diameter of said spring and less than four times the wire diameter of said spring.

5. The combination of claim 4 in which said deformation is formed in the segment from which said striker projects. 

1. In a photographic flashlamp unit having a plurality of percussively-ignitable flashlamps with primer tubes depending therefrom mounted on a base, a folded torsional firing spring for eaCh of said lamps disposed on said base, said firing spring comprising a substantially hairpin torsional section having two segments joined by a bight, a striker projecting from one of said segments, a supporting foot projecting from the other of said segments, and a catch formed at the tip of said foot, said striker crossing said foot and bearing against the segment from which said foot projects with said catch restraining said striker in a cocked condition, and one of said segments having a deformation located substantially adjacent to said striker between said bight and said striker, said deformation retaining said striker in firm engagement with the segment from which said foot projects.
 2. The combination of claim 1 in which said deformation in one of said segment tends to engage the other of said segments whereby said striker is retained in pivotal engagement with the segment from which said foot projects during cocking of said striker and, upon release of said striker from said catch, the travel of said striker is controlled to define a substantially circular arc about the segment from which said foot projects.
 3. The combination of claim 1 in which the diameter of said bight of said spring is equal to or less than 3 1/2 times the wire diameter of said spring.
 4. The combination of claim 1 in which the lateral excursion of said deformation is greater than one-half the wire diameter of said spring and less than four times the wire diameter of said spring.
 5. The combination of claim 4 in which said deformation is formed in the segment from which said striker projects. 